We have prepared monoclonal antibodies against polypeptides associated with human herpesviruses and have employed these reagents for carrying out structural analyses of the viral polypeptides. Emphasis has been placed on determining structural and antigenic differences between polypeptides coded by herpes simplex type 1 and 2, and in developing tests which would differentiate these viruse. This year we have prepared over 40 monoclonal antibodies against 8 different HSV-2 proteins, including the major capsid component, an early phosphoprotein, an early DNA binding protein, and the major glycoproteins of the virus. These antibodies are being used in conjunction with a similar group of HSV-1 monoclonals, which we had previously prepared, for antigenic and structural comparisons of the HSV proteins. Monoclonal reagents have been developed against a number of cell membrane proteins which appear to be associated with transformation, either viral induced or by DNA trasfection. The reagents will serve as diagnostic tools for the early identification of the transformed state.